Nitroxyl (HNO) has been shown to have positive cardiovascular effects in in vitro and in vivo models of failing hearts. However, at physiological pH, HNO dimerizes to hyponitrous acid, which subsequently dehydrates to nitrous oxide; due to this metastability, HNO for therapeutic use must be generated in situ from donor compounds. A variety of compounds capable of donating nitroxyl have been described and proposed for use in treating disorders known or suspected to be responsive to nitroxyl. See, e.g., U.S. Pat. Nos. 6,936,639; 7,696,373; 8,030,356; 8,268,890; 8,227,639; and 8,318,705 and U.S. pre-grant publication nos. 2009/0281067; 2009/0298795; 2011/0136827; and 2011/0144067. Although all of these compounds are capable of donating nitroxyl, they differ in various physicochemical properties, and there remains a need to identify nitroxyl donors that have physicochemical properties best suited for treating specific clinical conditions via specific routes of administration.
U.S. Pat. No. 8,030,056 describes the synthesis of derivatives of Piloty's acid type compounds that are capable of donating nitroxyl under physiological conditions and are useful in treating heart failure and ischemia/reperfusion injury. The nitroxyl donor CXL-1020 (N-hydroxy-2-methanesulfonylbenzene-1-sulfonamide) has been evaluated in a Phase I safety study in healthy volunteers and in a Phase IIa placebo-controlled, double-blind, dose-escalation study conducted at multiple hospitals. Sabbah et al., “Nitroxyl (HNO) a novel approach for the acute treatment of heart failure”, Circ Heart Fail., published online Oct. 9, 2013 (Online ISSN: 1941-3297, Print ISSN: 1941-3289). The studies demonstrated that in patients with systolic heart failure, CXL-1020, when administered intravenously as an aqueous solution at pH=4, reduced both left and right heart filling pressures and systemic vascular resistance, while increasing cardiac and stroke volume index. Hence, the studies demonstrated that CXL-1020 enhances myocardial function in human patients suffering from heart failure. However, at threshold doses of CXL-1020 needed to produce hemodynamic effects, the compound was found to induce side effects, including unacceptable levels of inflammatory irritation at and distal to the intravenous insertion site, and the authors report that because of such side effects, this compound would not be a viable candidate for a human therapeutic.
Accordingly, there is a need to develop new nitroxyl donating compounds (referred to herein as nitroxyl donors) and compositions that are useful for the treatment of heart failure and that have a suitable toxicological profile. Development of such compounds requires an understanding of the pharmacokinetic profile associated with nitroxyl donation and the factors influencing the toxicological profile. Failure to understand these factors has hampered the development of nitroxyl donors for clinical use.
Moreover, formulating nitroxyl donors has proven to be a considerable challenge. Many of the current nitroxyl donors are insoluble in aqueous solutions and/or are insufficiently stable. Solubility and stability problems often preclude the use of such compounds in pharmaceutical compositions for parenteral and/or oral administration. Accordingly, there exists a need to develop compositions containing nitroxyl donors at sufficient concentration for parenteral and/or oral administration that are sufficiently stable and have favorable pharmacological and toxicological profiles.
Citation of any reference in Section 1 of this application is not to be construed as an admission that such reference is prior art to the present application.